A temperature-compensated rotational position sensor based on fibre Bragg gratings

In this work a low-cost optomechanical rotational position sensor is presented. The sensing principle relies on monitoring the tangential strain of an elastic element by means of a fibre Bragg grating (FBG) glued on its surface. A second Bragg grating is used to provide compensation to temperature induced effects. The sensor prototype, calibrated in laboratory with both static and dynamic reference inputs, has shown excellent linear response, negligible hysteresis and good long term stability. An expanded uncertainty (at 95% confidence level) of 8.6 × 10−4 rad in the ±10° measurement range has been estimated according to ISO GUM. Key features of the proposed sensor are immunity with respect to electromagnetic noise and intrinsic wavelength encoded output signal, which can made it competitive for critical applications under severe environmental conditions.